A. Incorrect! It s not correct. Synergism of cytokines refers to two or more cytokines acting together.

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1 Immunology - Problem Drill 11: Cytokine and Cytokine Receptors Question No. 1 of A single cytokine can act on several different cell types, which is known as. Question #1 (A) Synergism (B) Pleiotropism (C) Antagonism (D) Autocrine action It s not correct. Synergism of cytokines refers to two or more cytokines acting together. B. Correct! Cytokines are pleiotropic in nature. Antagonism of cytokine refers to cytokines causing opposing activities. Cytokines bind to the receptors on the membrane of the same cell that secreted it is termed as autocrine action of cytokines. Cytokines are versatile molecules. They possess many different activities. One of them is pleiotropism. Cytokines are pleiotropic in nature. It is common for different cell types to secrete the same cytokine or for a single cytokine to act on several different cell types.

2 Question No. 2 of When a cytokine binds to its receptor, the signal is transduced and then what pathway is activated? The genes transcribed by this pathway are involved in the cell activation or in cell growth and differentiation. Question #2 (A) JAK-STAT pathway (B) Glycolysis pathway (C) Electron transport chain (D) All of the above A. Correct! That s right. JAK-STAT pathway is activated by the signal transduction after the binding of cytokine to its receptor. This pathway is not activated by cytokines. This pathway does not have the role of cytokines. There is one correct answer above. Try to remember the slide showing the basic model of cytokine action. When a cytokine binds to its receptor, the signal is transduced and the JAK-STAT pathway is activated. The end result of this pathway is to activate the transcription of certain genes, usually genes involved in cell activation or in cell growth and differentiation. Before this, the first step in cytokine signaling is ligand-induced aggregation of receptor components. The cytoplasmic regions of these receptor subunits interact to initiate a downstream signaling cascade to activate the specific pathway like JAK-STAT in this case.

3 Question No. 3 of Cytokines which binds to the receptors on a target cells in close proximity to the producer cell exhibit which mode of action? Question #3 (A) Autocrine (B) Endocrine (C) Paracrine (D) None of the above No, Autocrine action means Cytokines bind to the receptors on the membrane of the same cell that secreted it. Endocrine action refers to Cytokines bind to the receptors on a target cells in distant parts of the body. C. Correct! Yes, that s right. In paracrine action, cytokines bind to the receptors on a target cells in close proximity to the producer cell. There is one correct answer above. According to their mode of action cytokines are grouped as exerting autocrine, paracrine, and endocrine action. Paracrine action means, cytokines bind to the receptors on a target cells in close proximity to the producer cell. The terms autocrine, paracrine, and endocrine are themselves self illustrative.

4 Question No. 4 of Which one of the following cytokines belongs to the class-ii cytokine receptors? Question #4 (A) IFN- α (B) IL-8 (C) TNF- α (D) LIF A. Correct! That s right. IFN-α belongs to Class II cytokine receptors, which is also termed as Interferon (type 2) family. IL-8 belongs to chemokine receptors family and not class-ii family. It s not correct. TNF- α belongs to Tumor Necrosis Factor (TNF) receptors family. LIF is classified under the Class I cytokine receptors or Haemopoietic growth factor (type 1) family. To exert their biological effects, cytokines first bind to specific receptors expressed on the membrane of responsive target cells. Receptors for the various cytokines are quite diverse structurally, but almost all belong to one of five families of receptor proteins, given below: a. Immunoglobulin superfamily receptors b. Class I cytokine receptors c. Class II cytokine receptor family d. TNF receptor family e. Chemokine receptor family IFN- α, belongs to class II cytokine receptors or Interferon (type 2) family: the other members of this family include IFN β, IFN-γ and IL10. Prepare a chart of cytokine receptors and remember which cytokine comes under which family and also try to understand its function.

5 Question No. 5 of Several cytokines may have the same effect on the cells they bind; this process is known as. Question #5 (A) Redundancy (B) Pleiotropism (C) Synergism (D) Antagonism A. Correct! That s the right answer. Redundancy is the term used to describe this particular property. Pleiotropism refers to a single cytokine can act on several different cell types. It s not correct. When two or more cytokines act together, it is termed as Synergism. When cytokines cause opposing activities, it is termed as antagonism. Each cytokine binds to a specific cell-surface receptor and subsequent cascade of intracellular signaling takes place which alters cell functions like It increases the number of surface receptors for other molecules, Can suppress their own effect by feedback inhibition, It results in the production of other cytokines. Many cytokines can share these functions in common and hence they are characterized as redundant.

6 Question No. 6 of Conjugation of a toxin with a cytokine results in destruction of cells that are expressing one of the following receptors: Question #6 (A) TCR (B) BCR (C) BCR and TCR (D) Cytokine receptors Cytokines do not bind to TCR. Cytokines do not bind to BCR. No cell expresses both TCR and BCR together and also cytokines do not either of these receptors. D. Correct! That s right! Cytokines bind to cytokine receptors and as toxin is also bound to it, cell gets destructed. To exert their biological effects, cytokine must first bind to its specific receptor expressed on the membrane of responsive target cells. After binding to their specific receptors, cytokines can affect a diverse array of cells. Cytokine binding to its receptor induces dimerization or polymerization of receptor polypeptides at the cell surface & aids in transcription of the target gene. But the binding of toxin conjugated cytokine causes the destruction of the cell.

7 Question No. 7 of Which colony stimulating factor cytokine that also belongs to the class of hematopoietin receptors has been used as standard medical practice? Question #7 (A) Interferon (B) TNF- α (C) GM-CSF (D) IFN- α Interferon is used as a standard medical practice, but it does not belong to the class hematopoietin. TNF- α is not used as standard medical practice and also not in the class of hematopoietin. C. Correct! That s right. GM-CSF, which belongs to the class-i cytokine receptors (hematopoietin) is a colony stimulating factor used as a standard medical practice. IFN- α is used in the treatments of hepatitis and cancer, but it does not belong to the class of hematopoietin. Try to remember Therapeutic uses of Cytokines & their receptors. Each cytokine has a distinct function as a therapeutic agent. Try to classify these therapeutic cytokines according to their class of cytokine receptors they belong to. It will give more insight into their therapeutic function.

8 Question No. 8 of TNF-β is produced by which of the following cells that is involved in cell mediated inflammatory responses? Question #8 (A) T H 1 cell (B) T H 2 cell (C) TC cell (D) B cell A. Correct! That s right. T H 1 cells produce TNFβ along with IFNγ & IL-2 and are involved in the cell mediated inflammatory responses. T H 2 cells do not produce TNFβ and they are also not involved in the cell mediated inflammatory responses. TC cells do not produce TNFβ. It is the property of T H cells. B cells do not produce cytokines, they produce antibodies. Go through the slides describing the functions of Cytokine secretion by T H 1 & T H 2 subsets. CD4+ T H cells have two different profiles of cytokines production T H 1 & T H 2. TH1 includes IFNγ, TNFβ & IL-2. T H 1 are involved in cell-mediated inflammatory reactions, they activate cytotoxic, & delayed hypersensitivity reactions. T H 2 produce IL-4, IL-5, IL-6, IL-9, IL-10, IL-13. It encourages the production of antibody especially IgE. They are associated with regulation of strong antibody & allergic responses. Cytokines from T H 1 cells inhibit the actions of T H 2 cells & vice versa.

9 Question No. 9 of Cytokine binds to its receptor on the cells and induces dimerization or polymerization of receptor polypeptides at the cell surface causing the activation of intracellular signaling pathways (e.g. kinase cascades). What is produced by the activation of these signaling pathways? Question #9 (A) Translation factors (B) Cytokines (C) Antibodies (D) Transcription factors It s a wrong answer. Try again. Cytokines are not produced by the activation of these signaling pathways. The substances produced by the activation of these signaling pathways induce certain genes. Antibodies are not produced by the activation of these signaling pathways. The substances produced by the activation of these signaling pathways induce certain genes. D. Correct! Transcription factors are produced by the activation of these signaling pathways which activate genes involved in the cell activation or in cell growth and differentiation. Try to understand the Basic model of cytokine action. The first step in cytokine signaling is ligand-induced aggregation of receptor components. The cytoplasmic regions of these receptor subunits interact to initiate a downstream signaling cascade. When a cytokine binds to its receptor, the signal is transduced and the JAK-STAT pathway is activated. The end result of this pathway is to activate the transcription of certain genes, usually genes involved in cell activation or in cell growth and differentiation.

10 Question No. 10 of Which one of the following is not the property of cytokines? Question #10 (A) Act synergistically (B) Pleiotropic in nature (C) Exert autocrine action (D) None of the above Cytokines act synergistically. Cytokines show Pleiotropic in nature. Cytokines exert autocrine action. D. Correct! That s right. All these three properties are displayed by the cytokines. Cytokines are a group of small secreted proteins and peptides that are used in organisms as signaling compounds. They are involved in variety of processes like; inflammatory immunological, infectious diseases & in embryogenesis. While performing all these functions they display various properties. Many cytokines can share similar functions; hence they are characterized as redundant. Cytokines are pleiotropic (It is common for different cell types to secrete the same cytokine or for a single cytokine to act on several different cell types) in nature. Cytokines can also act synergistically (two or more cytokines acting together) or antagonistically (cytokines causing opposing activities). Go through the tutorial meticulously and remember all the properties of cytokines.